Join the QSFP28 optical module OSFP

QSFP28 modules cannot be directly inserted into OSFP ports due to physical and electrical incompatibility, but interoperability may be achieved through adapters or compatible optical standards.

Key Differences Between QSFP28 and OSFP

• Form Factor and Size: QSFP28 is a compact 4-lane module supporting 100G Ethernet, while OSFP is larger, designed for 8-lane high-speed signals supporting 400G and beyond, with better heat dissipation and higher power envelopes (up to ~16 W) .
• Lane Configuration: QSFP28 uses 4 lanes at 25 Gbps each (total 100G), whereas OSFP supports 8 lanes, each capable of 50G PAM4 (400G) or higher .
• Physical Compatibility: OSFP and QSFP-DD ports are different in cage design and connector layout. QSFP28 modules are smaller and cannot fit directly into OSFP cages .
• Thermal and Power Considerations: OSFP modules are designed for higher power consumption and advanced thermal management, which QSFP28 modules do not require .

Interfacing Options

1. Adapters or Breakout Cables: While direct insertion is impossible, some optical adapters or breakout cables can allow QSFP28 modules to interoperate with OSFP systems if both support the same Ethernet standard (e.g., 100G over 4×25G lanes) .
2. Optical Interoperability: QSFP28 modules can communicate with OSFP modules optically if the fiber type, wavelength, and signaling standard match, but electrical pin compatibility is not guaranteed .
3. Migration Strategy: For data centers upgrading from 100G QSFP28 to 400G OSFP, it is common to maintain QSFP28 modules on legacy ports while deploying OSFP modules on new high-speed ports, using optical splitters or breakout cables for connectivity .

Practical Considerations

• Check Vendor Compatibility: Not all QSFP28 modules are interchangeable with OSFP systems, so verify vendor specifications and supported standards .
• Thermal Management: Ensure airflow and heat dissipation are adequate when using adapters or mixed module deployments .
• Electrical Signaling: QSFP28 uses 25G NRZ per lane, while OSFP may use PAM4 signaling for higher speeds; mismatched signaling can prevent proper operation .

Summary

Directly joining a QSFP28 module to an OSFP port is not possible due to physical and electrical differences. Interoperability requires adapters, breakout cables, or optical standard alignment, and careful attention to power, thermal, and signaling compatibility. For 100G deployments, QSFP28 remains suitable, while OSFP is intended for 400G and future high-speed networks .